Optical illusion spooks raptors

October 11, 2018, CNRS
Display showing deterrent pattern at Lourdes-Tarbes-Pyrenees. Credit: Anthony Boigné

Researchers from the CNRS and Université de Rennes 1, in collaboration with Airbus, have designed a visual pattern that elicits long-term avoidance of high-risk areas by raptors. The work clears the way for further investigation into the visual cognition of these birds, and it has applications for conservation, because raptors are among the most common victims of collisions with planes and wind turbines. Their findings are published in PLOS ONE.

Despite their exceptional visual acuity, raptors cannot detect some obstacles like glazed surfaces, and are too late in detecting certain moving objects, like planes. In France, over 800 collisions of birds with planes are reported each year. As available deterrent systems are ineffective with raptors, scientists from the Éthologie Animale et Humaine (Ethos) research laboratory sought to develop a new means of repelling these birds from specific areas.

Applying current knowledge about vision in these species, the team first observed how captive raptors reacted to a series of . After over 300 tests, they concluded that only one pattern triggered by virtue of an optical illusion. This 'superstimulus' consists of concentric black circles on a white background. It creates a so-called 'looming' effect, giving the birds the impression of an imminent collision.

The pattern was tested at Lourdes-Tarbes-Pyrénées Airport, near plains where raptors like buzzards and kites forage in the summer. It was displayed continuously throughout the day on two LED screens positioned in strategic locations, while a total of 8,800 observations were made at points all over the airport zone. The team detected a rapid modification of the birds' distribution: they stayed clear of areas from which the screens were visible. This avoidance behavior was still observable after five weeks of continuous pattern display.

The fact that the population rose in places where the displays were out of view, at a time when their food supply was nonetheless abundant in all areas, is proof of the pattern's efficacy. Interestingly, the visual stimulus triggered similar behavior among corvids at the site, but not other passerines. These findings are the first to describe a harmless, sustainable solution for repelling raptors from high-risk areas. They also suggest new areas of research, such as the possible role played in this behavior by collision-detecting neurons, specialized in avoidance reactions.

Explore further: Millions of birds die in collisions each year, but lights could change that

More information: PLOS ONE (2018). DOI: 10.1371/journal.pone.0204802

Related Stories

The raptors guarding Mexico City's airport

February 2, 2018

Far from the crowds of passengers, lines and passport control, Madison spreads his wings on the side of a runway at Mexico City's international airport, the busiest in Latin America.

Colour vision makes birds of prey successful hunters

August 29, 2018

In many cases it is the colour of the prey that helps predatory birds to detect, pursue and capture them. In a new study, biologists at Lund University in Sweden show that the Harris's hawk has the best colour vision of all ...

Recommended for you

Meteorite source in asteroid belt not a single debris field

February 17, 2019

A new study published online in Meteoritics and Planetary Science finds that our most common meteorites, those known as L chondrites, come from at least two different debris fields in the asteroid belt. The belt contains ...

Diagnosing 'art acne' in Georgia O'Keeffe's paintings

February 17, 2019

Even Georgia O'Keeffe noticed the pin-sized blisters bubbling on the surface of her paintings. For decades, conservationists and scholars assumed these tiny protrusions were grains of sand, kicked up from the New Mexico desert ...

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

carbon_unit
5 / 5 (2) Oct 11, 2018
Wonder if this could be used around wind farms too.
Whydening Gyre
4 / 5 (1) Oct 11, 2018
Paint it on the blades...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.